A vehicle may comprise a robot that is used indoors, for example. In an indoor environment, reliable positioning data from a Global Positioning System (GPS) receiver with differential correction may not be available because of attenuation from a building or otherwise. Radio frequency beacons may produce unreliable or anomalous position readings indoors because of reflections, multi-path reception, attenuation, or other propagation issues.
Visual landmarks may provide inconsistent position information because of visual obstruction of the landmark, aliasing with similar landmarks, or corruption of the appearance of the visual landmark. For example, the distinguishing features of the visual landmark might be damaged or corrupted by mechanical contact with equipment or other items in a warehouse environment. Accordingly, there is a need for reliably determining the position of a vehicle with respect to a landmark (e.g., a visual landmark).